An Estimate of the Reduction Potential of B(C6F5)3 from Electrochemical Measurements on Related Mesityl Boranes

MesB(C 6 F 5 ) 2 ( 1 ) has been prepared from MesMgBr and FB(C 6 F 5 ) 2 ·OEt 2, while Mes 2 B(C 6 F 5 ) ( 2 ) is readily available from CuC 6 F 5 and Mes 2 BBr. The reduction potential E ° of 1 vs Cp 2 Fe 0/+ in THF is −1.72 V, while that of 2 is −2.10 V, and that of Mes 3 B ( 3 ) is −2.73 V. 11 B and 1 H NMR show that neither 1 nor 2 binds THF significantly. These results have been used to estimate the reduction potential of B(C 6 F 5 ) 3 in THF as −1.17 V vs Cp 2 Fe 0/+ or as −0.64 V vs SCE.